1. Field of the Invention
The present invention relates generally to center pivot and lateral move irrigation systems. More specifically, the present invention relates to a remote monitoring unit which senses movement or non-movement of the irrigation system over a span of time to determine operating status (running or stopped), to determine pivot arm position (e.g., location of last wheel set) and to remotely sense water delivery through the span pipes to determine wet/dry status. The remote monitoring unit is self-contained without having to hard-wire directly to any existing control or other electrical circuits of the irrigation system.
2. Discussion of the Background
Mechanized sprinkler irrigation systems, such as center pivot and lateral move irrigation systems, are commonly used and almost 200,000 exist in the United States alone. Typical systems irrigate over 100 acres to as high as 600 acres. Factors such as soil type, soil water intake rate, slope, water availability, energy costs, flotation for wheels and land obstacles affect the use of such systems. Large farms with scattered field sites and multiple crops are typical users of center pivot and lateral or linear move mechanized irrigation systems. Manually monitoring such systems by “on site inspections” has been the norm. Two to three daily on site visits by 4WD pickup truck, SUV or ATV are considered minimal to observe and respond to shutdowns and breakdowns and to maintain irrigation schedules that meet crop water requirements. An unnoticed shutdown may result in substantial loss of the crop.
Center pivot irrigation systems typically are set up to apply a specific amount of water to the whole field (one 360 degree rotation). Such applications typically take three to four days to complete and longer for larger fields. Therefore, the amount of changes to the pivot setup is infrequent (one or two per week, driven by weather and crop growth stage). In terms of remote control and monitoring, the primary need is to know “status”; i.e., is the irrigation system running (moving), with or without water and has it shutdown? Unplanned stoppages are common due to field conditions (stuck wheels) and mechanical and electrical malfunction (broken drive lines, failed electro-mechanical devices, etc.). Water delivery systems also breakdown and cause irrigation systems to stop. Electrical power outages and deliberate load shed schemes by power providers can cause hundreds of irrigation systems to shutdown at any hour of the day. Water delivery systems powered by natural gas engines are subject to gas line pressure fluctuations that can cause internal combustion engines to shutdown, resulting in loss of water delivery and a center pivot shutdown. Mechanized irrigation systems need to be monitored 24/7 to maintain critical watering schedules for optimum yield and crop quality.
Over the last twenty-five years several remote monitoring systems have been put to commercial use. All use telemetry and all require a wired interface between the control circuitry of the center pivot main panel and the digital and analog inputs to the monitoring device, typically called a remote terminal unit (RTU). Typical RTUs include either a hard wire connection to telephone circuits or a wireless radio for remote communication. Telemetry systems sold by irrigation system manufacturers often include electronic and programmable center pivot main panels (or other hardware retrofits) at the center pivot point with radio telemetry paths to on-farm “base station” computers, running proprietary software. Most include remote control functions and some monitor pivot position using an electronic encoder or resolver, rotated at the pivot center point by the movement of the first drive tower, to sense pivot arm position in degrees from north at the front of the center pivot. The pivot arm position, in turn, is used by a programmed set of instructions stored in the pivot main panel or at a base station computer to initiate control changes based on pivot arm position such as pivot speed changes, pivot direction changes, turning the pivot off, end guns on, etc.
Recent developments by center pivot manufacturers and others have been to use one or two GPS receivers in-lieu-of the mechanical encoder or resolver heretofore used with the “programmable” main panels to determine pivot arm position (azimuth from the center pivot point or a starting point for a lateral move sprinkler) and, thereby, control the functions of a center or lateral move sprinkler based on pivot arm position.
U.S. Pat. No. 6,512,992 (Fowler, et al, Inventor; Raven Industries, Inc., assignee) refers to a GPS-based control system for irrigation using two GPS receivers. This system claims an improved “positioning” and alignment system by using GPS and differential GPS (DGPS) methods to monitor the absolute and/or relative position of a selected location near the end of the pivot arm referenced from a fixed, known position of a central tower (center pivot point). Fowler describes a device to determine pivot arm position (azimuth and the distance between the fixed center point and the end of the moving pivot arm) using two GPS receivers, one at the fixed center pivot point and a second at the end of the moving pivot arm. The two GPS receivers (one or both with “differential” GPS) communicate with each other to remove GPS errors. Fowler also claims a device to detect the degree of “misalignment” of drive towers along the pivot arm using the two GPS receivers. Fowler further claims a method of controlling the plurality of reversible drive motors (one at each drive tower) to maintain alignment of the jointed pipe spans making up the length of the pivot arm. Fowler also claims a method of monitoring the degree of misalignment in order to identify failed drive towers.
U.S. Patent Application Publication U.S. 2004/0117070 (Luke J Barker, inventor; Reinke Manufacturing Co., Inc., assignee) refers to a GPS-based control system for irrigation that uses a single GPS receiver at the end of the pivot arm. This GPS receiver has stored in memory coordinates for the fixed GPS position of the center pivot point. Using the stored reference GPS coordinates of the center point along with the roving GPS receiver's coordinates facilitates calculation of the pivot arm azimuth with a single GPS receiver. Barker asserts that there is a need for an improved control system for center pivot and lateral move sprinklers that use GPS to accurately detect the angular position of a center pivot arm and to accurately detect the distance traveled by a lateral move sprinkler, and that uses such information to control various functions of the irrigation system. The control system receives the two GPS position coordinates (one fixed and stored, the other from the roving GPS receiver at the end of the pivot arm) and communicates with the center pivot main panel to control a function of the irrigation system, such as stopping, reversing, end gun operation, application rate, etc., at a selected distance (lateral move sprinkler) or azimuth value (center pivot).
Without regard to the type of main panel or the degree of programmability based on pivot arm position, the prior art method of remotely monitoring on/off status is to monitor by radio the electric control circuitry with digital inputs interfaced and hard wired from a remote terminal unit (RTU) to the electrical circuitry of the center pivot control panel located at the fixed center pivot point. This requires electrical connections inside the center pivot main panel. Because there are many brands and models of center pivots in use, many with unique control circuitry, a degree of expertise and electrical wiring competency is required for safe and correct installation that provides the needed functionality and meets the requirements of the National Electrical Code for Center Pivot and Lateral Move Sprinklers. Furthermore, the sensitive electronics and radios needed to remotely monitor pivot status by this hard-wired method are easily interfered with and can be damaged from improper installation, electrical power surges and lightning events. As a result, the systems tend to be costly to manufacturer, install and maintain.
These types of remote monitoring and control systems are expensive and are often impractical on older pivots without extensive upgrades to the pivot point and the pivot controls. Often older pivot control circuitry has been field modified over years of maintenance. Many lack proper documentation to facilitate the proper interface of circuitry wires required with traditional remote monitoring devices.
A need therefore exists for a universal remote terminal unit (RTU) that does not interface with the AC control or AC power wiring of the mechanized irrigation system. A need further exists to self-contain the RTU with independent power, and with the ability to independently detect movement and non-movement and/or water delivery status and to transmit such status changes to a remote location in a format that is easily understood by the operator of the mechanized irrigation systems. A need further exists for a universal RTU that is simple to install, without electrical wiring know-how and is simple to relocate to alternative center pivots for maximum utility and cost effectiveness. A need further exists for a wireless device for determining pivot position (azimuth of the pivot arm around the center point or the location of a lateral move sprinkler) using a single GPS receiver at or near the end of the pivot arm.